1. Field of the Invention
The present invention relates to methods for manufacturing color filters, and apparatuses for carrying out the methods. Particularly, the present invention relates to a method and an apparatus for manufacturing color filters suitably used in liquid-crystal display units, and more particularly, relates to a method and an apparatus for manufacturing color filters based on a manner in which electrodes are brought into contact with a deposition solution comprising an electrolytic solution and a pigment material dispersed therein, and color layers are thereby formed on the electrodes, as in a Micelle electrolyzing method, a electro-deposition method, or the like.
2. Description of Related Art
Generally, in a liquid-crystal display unit, a transparent conductive film comprising, for example, ITO (Indium Tin Oxide) is formed on each surface of a pair of transparent substrates, a plurality of pixel electrodes are constructed with the transparent conductive film, predetermined voltages are selectively applied to some of the pixel electrodes, and thus visible information such as characters and figures is displayed.
In recent years, color-displaying has been increasingly introduced in liquid-crystal display units. In some cases, in order to achieve color-displaying, color filters are formed by coating such pixel electrodes with color layers in the process for manufacturing liquid-crystal display units. Such a method for forming color filters is generally called a COI (Color Filter On ITO) method.
Hitherto, a dyeing method, a printing method, a pigment-dispersing method, an electro-deposition method, and other various methods have been known as methods for coating with color layers. Additionally, a so-called Micelle electrolyzing method as disclosed in Japanese Unexamined Patent Publication No. 2-267298 is known as one of these methods.
In the Micelle electrolyzing method, for example, as shown in FIG. 9, a transparent substrate 102 is dipped in a deposition solution 101 prepared by dispersing a pigment material in an electrolytic solution, a pixel electrode 103 on the transparent substrate 102 is made to serve as an anode while a submerged electrode 104 disposed in the deposition solution 101 is made to serve as a cathode, and the deposition solution 101 is electrolyzed to form a color layer on the pixel electrode 103.
According to the Micelle electrolyzing method, since a color layer is selectively formed on the pixel electrode as an anode to which a voltage is applied, the treatment is easy and deposition accuracy is high. Further, since deposition proceeds by electrolysis, the thickness of the deposited film can be controlled depending on the applied electric charge quantity.
In this conventional method, however, since the voltage is applied to only one end portion of the transparent pixel electrode 103, the color layer becomes thick near the portion for voltage application while it gradually becomes thin in proportion to the distance from the portion. Further, since such thickness irregularity of the color layer in proportion to the distance from the voltage-applied portion is based on the resistance value of the electrode pattern, the thickness irregularity of the color layer further increases in response to the thickness irregularity of the transparent pixel electrode. Moreover, in deposition, by applying electricity to only one end of the transparent substrate, deposition efficiency is low relative to applied electric current due to the resistance of the pixel electrode pattern.
The present invention has been accomplished in view of the above-described problems, and its object is to provide a method and an apparatus for manufacturing color filters, by which the color layer can be formed so as to have a uniform thickness, the thickness can be highly accurately controlled, and deposition efficiency relative to applied electric current can be improved.